The following code emulates exactly the behavior of pointers in C:
from collections import deque # more efficient than list for appending things
pointer_storage = deque()
pointer_address = 0
class new:
def __init__(self):
global pointer_storage
global pointer_address
self.address = pointer_address
self.val = None
pointer_storage.append(self)
pointer_address += 1
def get_pointer(address):
return pointer_storage[address]
def get_address(p):
return p.address
null = new() # create a null pointer, whose address is 0
Here are examples of use:
p = new()
p.val = 'hello'
q = new()
q.val = p
r = new()
r.val = 33
p = get_pointer(3)
print(p.val, flush = True)
p.val = 43
print(get_pointer(3).val, flush = True)
But it's now time to give a more professional code, including the option of deleting pointers, that I've just found in my personal library:
# C pointer emulation:
from collections import deque # more efficient than list for appending things
from sortedcontainers import SortedList #perform add and discard in log(n) times
class new:
# C pointer emulation:
# use as : p = new()
# p.val
# p.val = something
# p.address
# get_address(p)
# del_pointer(p)
# null (a null pointer)
__pointer_storage__ = SortedList(key = lambda p: p.address)
__to_delete_pointers__ = deque()
__pointer_address__ = 0
def __init__(self):
self.val = None
if new.__to_delete_pointers__:
p = new.__to_delete_pointers__.pop()
self.address = p.address
new.__pointer_storage__.discard(p) # performed in log(n) time thanks to sortedcontainers
new.__pointer_storage__.add(self) # idem
else:
self.address = new.__pointer_address__
new.__pointer_storage__.add(self)
new.__pointer_address__ += 1
def get_pointer(address):
return new.__pointer_storage__[address]
def get_address(p):
return p.address
def del_pointer(p):
new.__to_delete_pointers__.append(p)
null = new() # create a null pointer, whose address is 0